Method for tight control of bolt holes in fan assembly

Abstract

In a fan case having an annular outer wall with a plurality of fan case bolt holes there through, bushings are inserted into the fan case bolt hole and are dimensioned to define an annular gap between the bolt hole inner surface and the bushing outer surface. An adhesive material disposed within each annular gap between the bushing and the corresponding fan case bolt hole, with the adhesive material forming a liquid shim separating the bushing outer surface from the bolt hole inner surface.

What is claimed is: 
     
       1. A fan case assembly for a gas turbine engine, comprising:
 a fan case having an annular outer wall and an annular sleeve disposed on an outer surface of the annular outer wall, the annular outer wall and the annular sleeve having a plurality of fan case bolt holes extending therethrough, wherein each of the plurality of fan case bolt holes has a bolt hole inner surface having a bolt hole inner diameter; 
 a plurality of bushings each having a cylindrical body having a bushing inner surface defining a cylindrical bore having a bushing inner diameter and a bushing outer surface with a bushing outer diameter that is less than the bolt hole inner diameter, wherein the cylindrical body of each of the plurality of bushings is inserted into a corresponding one of the plurality of fan case bolt holes with an annular gap being defined between the bolt hole inner surface and the bushing outer surface, wherein each of the plurality of bushings has a top edge and comprises a flange extending radially outwardly from the cylindrical body at the top edge and having a flange outer diameter that is greater than the bolt hole inner diameter, wherein the flange of each of the plurality of bushings directly contacts an outer surface of the annular sleeve; and 
 an adhesive material disposed within the annular gap between each one of the plurality of bushings and the corresponding one of the plurality of fan case bolt holes, wherein the adhesive material forms a liquid shim separating the bushing outer surface from the bolt hole inner surface of the corresponding one of the plurality of fan case bolt holes. 
 
     
     
       2. The fan case assembly according to  claim 1 , wherein the adhesive material comprises an epoxy paste adhesive. 
     
     
       3. The fan case assembly according to  claim 1 , wherein the plurality of fan case bolt holes comprise:
 a first row of fan case bolt holes parallel to and proximate an aft edge of the fan case; and 
 a second row of fan case bolt holes parallel to the aft edge of the fan case and positioned forward of the first row of fan case bolt holes relative to the aft edge of the fan case. 
 
     
     
       4. The fan case assembly according to  claim 1 , comprising a plurality of structural guide vanes each having a plurality of guide vane bolt holes, wherein the guide vane bolt hole for each of the plurality of structural guide vanes are positioned to axially align with corresponding fan case bolt holes. 
     
     
       5. The fan case assembly according to  claim 4 , wherein a guide vane bolt hole inner diameter for each of the plurality of guide vane bolt holes is approximately equal to the bushing inner diameter of the cylindrical body. 
     
     
       6. The fan case assembly according to  claim 4 , comprising a plurality of fasteners, with each fastener being inserted through one of the plurality of guide vane bolt holes and the corresponding cylindrical bore of one of the plurality of bushings to secure the structural guide vane to the annular outer wall of the fan case. 
     
     
       7. The fan case assembly according to  claim 4 , wherein each of the plurality of structural guide vanes comprises a guide vane base having the plurality of guide vane bolt holes extending therethrough.